TORONTO — Elena Dementieva of Russia advanced to the final of the Rogers Cup on Saturday with a 7-6 (2), 6-1 win over Serena Williams.

Dementieva, the tournament's fourth seed, will face either Maria Sharapova and Alisa Kleybanova in Sunday's championship match.

The second-seeded Williams came into the match as the hottest player in the tournament, but an unreliable serve and a litany of unforced errors were her undoing. The 2001 Rogers Cup champion was broken five times and looked out of rhythm from the start, hitting routine shots long, wide or into the net.

With the win, Dementieva avenged her loss to Williams in the semifinals at Wimbledon, a three-set classic that took nearly three hours to play. She has beaten Williams in four of their last five hardcourt meetings, a positive sign for Dementieva with the U.S. Open getting under way in just over a week.

Williams entered Saturday having been broken just once in her first three matches — and it was the only break point opportunity she had allowed all tournament. But she struggled from the outset against Dementieva, giving up a break in the third game of the match.

The players traded several more breaks — six in total — before Dementieva prevailed in the tiebreaker. She opened up a 4-1 lead and eventually captured the set when Williams hit a forehand long. It was the first set Williams had lost all tournament.

Dementieva broke Williams early in the second set to jump ahead 2-0 and held serve the rest of the way as a frustrated Williams continued to pile on the unforced errors. The match ended when Williams pushed a forehand wide.